I already answered this question but the explanation might not be that clear. Reposted below:
a. 'Fire department' is tricky; a fire department has lots of people working in it, but is a 'group noun', meaning that it's singular even though it refers to more than one person. But as it is singular, we would use 'it' instead of 'they', so this is incorrect.
*The SAT will try to trick you a lot with group nouns, which are actually singular. Be careful.
b. 'Its' is used correctly as singular. There's nothing else wrong ; this option is definitely one to consider.
c. 'Them' is ambiguous .. Who or what does it point to? The fire department as a whole? Or workers within it? Ambiguity is something to avoid. Also, if it referred to the department, we would use 'it'.
d. Again, fire department is singular, so we would use 'its' and not 'their'. But even if we substituted in 'its', the word is unnecessary.
e. More singular-plural tricks: Here, the subject is 'result' (singular) and yet, the verb is 'are' (plural). We would either need 'the result is' or 'the results are'.
Concepts were kind of brushed over - I can explain the different grammar rules more in-depth if that helps?